Clinical characteristics and molecular genetics of seven neonates with congenital nephrogenic diabetes insipidus / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical characteristics, genetic basis and clinical treatment of seven neonates with congenital nephrogenic diabetes insipidus (NDI).@*METHODS@#Clinical data of the patients were collected. High-throughput sequencing was carried out to detect potential variants. Sanger sequencing was used to verify the results.@*RESULTS@#The patients were all males, with the age of onset being 10 to 21 days. All patients were admitted to the hospital for intermittent fever as the first symptom during the neonatal period. Additional symptoms had included polydipsia and polyuria. After the treatment, 5 patients had recovered, the remainders still had NDI symptoms and developmental retardation. Five children were found to harbor pathogenic variants of the AVPR2/AQP2 gene, which included one in-frame mutation of c.645_646insGCACCTACCCTGGGTATCGCC, two missense mutations of c.541C>T and c.419C>A, and two hemizygous deletions of the AVPR2/AQP2 gene. Among these, two were unreported previously. Cases 6 and 7 were a pair of twins. Both had carried homozygous missense variants of c.538G>A of the AVPR2/AQP2 gene, which was known to be pathogenic.@*CONCLUSION@#AVPR2/AQP2 is the main pathogenic gene for congenital NDI, for which two novel pathogenic variants have been discovered in this study. Above results have provided a basis for clinical diagnosis and genetic counseling for the affected pedigrees.

Analysis of AVPR2 variant in a neonate with congenital nephrogenic diabetes insipidus / 中华医学遗传学杂志

OBJECTIVE@#To detect potential variant in a male neonate affected with congenital nephrogenic diabetes insipidus (CNDI).@*METHODS@#Clinical data of the patient was collected. Genomic DNA was extracted from peripheral blood samples from the child and his parents. The whole coding regions of the arginine vasopressin V2 receptor (AVPR2) gene were amplified by PCR and subjected to Sanger sequencing.@*RESULTS@#The patient presented recurrent fever and polyuria after birth. Multiple blood gas analyses indicated hypernatremia. Ultrasound showed bilateral hydronephrosis and hydroureter. The patient was partially responsive to hydrochlorothiazide. DNA analysis identified a hemizygous frameshift variant c.890-899delACCCGGAGGC in exon 2 of the AVPR2 gene in the proband. His mother was heterozygous for the same variant.@*CONCLUSION@#The c.890-899delACCCGGAGGC variant of the AVPR2 gene probably underlies the CNDI in the child. Above discovery has enriched to spectrum of CNDI associated variants.

Nephrogenic diabetes insipidus (NDI): clinical, laboratory and genetic characterization of five Brazilian patients

INTRODUCTION: Nephrogenic diabetes insipidus is characterized by a lack of response in the distal nephron to the antidiuretic hormone arginine vasopressin. Manifestations include polyuria, polydipsia, hyposthenuria, recurrent episodes of dehydration and fever and growth failure. Most cases are caused by mutations in the AVPR2 gene. The mutant receptors are trapped intracellularly. METHOD: We studied five boys using clinical, laboratory and molecular data. The mean age at diagnosis was 14.6 months (range 6 to 24) and 12.2 years (7.8 to 19) after the follow-up period. The mean period of follow-up was 132.2 ± 50.9 months. RESULTS: The geometric means of the z-scores of weight and stature were -4.5 and -3.6, respectively, at diagnosis. At the last medical appointment, the z-scores of weight and stature were -0.3 and -0.9, respectively. Three patients were diagnosed with ureterohydronephrosis and exhibited increased post-void urine volume. Mutations in the AVPR2 gene were found in all patients, and the carrier status was confirmed in four of five cases. Two unrelated children presented identical mutations (S167L) in arginine vasopressin R2. Two of the patients had a mutation that has already been described in other Brazilian families (R337X), and one patient showed a de novo mutation (Y128D) in arginine vasopressin R2, since his mother's molecular analysis was normal. The recurrence risk for this family was significantly reduced. CONCLUSION: This study reports the clinical and laboratory characterization of Nephrogenic diabetes insipidus and reiterates the importance of the genetic basis that underlies the disease diagnosis and genetic counseling.

Diabetes insipidus nefrogênico: conceitos atuais de fisiopatologia e aspectos clínicos / Nephrogenic diabetes insipidus: actual concepts of fisiopathology and clinical aspects

O diabetes insipidus nefrogênico (DIN) é uma doença rara caracterizada pela incapacidade do rim de concentrar a urina, a despeito de concentrações normais ou aumentadas do hormônio antidiurético arginina-vasopressina (AVP). Recentes avanços da fisiopatologia renal mostraram que, após a ligação do AVP ao seu receptor AVPR2 (receptor de vasopressina tipo 2), uma cascata de eventos culmina com a reabsorção de água no túbulo coletor, por meio de canais permeáveis exclusivamente à água e localizados nas membranas apicais do túbulo coletor, sendo o mais importante deles a aquaporina-2 (AQP2). A identificação, caracterização e análise mutacional dos genes AVPR2 e AQP2 permitiram estabelecer as bases moleculares de vários tipos hereditários de diabetes insipidus nefrogênico. Aproximadamente 90 por cento desses pacientes apresentam mutações do AVPR2, 8 por cento apresentam mutações no AQP2 e o restante não tem causas identificadas. Nessa revisão apresentamos exemplos de alterações genéticas e sugerimos que o uso de técnicas de biologia molecular pode minimizar as complicações dessa doença heterogênea mas com fenótipo bastante semelhante.

A novel polymorphism in the coding region of the vasopressin type 2 receptor gene

Nephrogenic diabetes insipidus (NDI) is a rare disease characterized by renal inability to respond properly to arginine vasopressin due to mutations in the vasopressin type 2 receptor (V2(R)) gene in affected Kindreds. In most Kindreds thus far reported, the mode of inheritance follows an X chromosome-linked recessive pattern although autosomal-dominant and autosomal-recessive modes of inheritance have also been described. Studies demonstrating mutations in the V2(R) gene in a affected Kindreds that modify the receptor structure, resulting in a dys- or nonfunctional receptor have been described, but phenotypically indistinguishable NDI patients with a structurally normal V2(R) gene have also been reported. In the present study, we analyzed exon 3 of the V2(R) gene in 20 unrelated individuals by direct sequencing. A C(T alteration in the third position of codon 331 (AGC(AGT), which did not alter the encoded amino acid, was found in nine individuals, including two unrelated patients with NDI. Taken together, these observations emphasize the molecular heterogeneity of a phenotypically homogeneous syndrome.